The present invention relates to an engine generator including an engine and a power generating body driven by the engine. More particularly, the present invention relates to an engine generator which allows a power generating body based on one control system to be replaced with another power generating body based on another control system.
An automatic voltage regulator (AVR) using a capacitor and the like has widely been used for a control system for controlling a generated voltage in a engine generator. Recently, highly accurate voltage stability and frequency characteristic are required also for the engine generator. In this circumstance, the number of engine generators each employing a control system of an inverter type is on the increase.
In the engine generator of the AVR type, a magnet of the power generating body has two poles. Accordingly, to produce electric power at 60 Hz, the engine is rotated at 3600 rmp. The control unit is relatively small in size.
On the other hand, in the engine generator of the inverter type, a rotor provided with a magnet having at least 20 poles is rotated at high speed, so that it is capable of generating higher electric power than that generated by the conventional engine generator of the AVR type. As a result, the electronic parts of the control unit are large in size, and the control unit per se is also large.
Thus, the structures of the engine generators based on both the control systems are greatly different from each other. Accordingly, even in a design of only the control units of the engine generators, it is difficult to design them so as to satisfy common specifications. For this reason, it is a general practice of the engine generator design to employ either of the control systems for its control system. Accordingly, also in production and sales stages, a manufacturer is obliged to grasp the demands of both the control systems, and then to manufacture and purchase the related merchandize. Excessive stock or shortage of merchandize in stock is likely to occur, and it is difficult to secure an optimum stock.
However, the engine generator may be categorized into two types depending on an interior structure thereof. A first type of the engine generator is structured such that, as disclose in Japanese Patent Unexamined Publication No. Hei. 8-223854, one end part of a crank shaft of the engine is used as an output shaft thereof. The power generating body is provided on the output shaft, whereas a recoil starter is provided on the other end. Namely, in this type of the engine generator, component parts are disposed on both sides of the engine. The part layout is easy in this type, so that a structure of the device is relatively simple.
A second type of the engine generator is structured such that one end part of the crank shaft is used as an output shaft thereof, and the power generating body and the recoil starter are mounted on the output shaft. This type of the engine generator is more complex in structure than the first type of the engine generator, but the whole device is made compact advantageously.
In the second type of engine generator, the number of mounting parts is large. This necessitates use of a long dedicated crank shaft. This hinders the use of the general purpose engine for the engine generator. Even when the dedicated parts are used, the flywheel and the cooling fan are mounted on the tapered part of the crank shaft, and the power generating body is mounted at a position subsequent to them. For this reason, in the power generating body mounting part, it is impossible to secure a sufficient tapered shaft diameter.
Accordingly, it is an object of the present invention to provide an engine generator which allows the control system to be replaced with another type control system by easy replacing work.
The object of the present invention can be achieved by an engine generator, according to a first aspect of the present invention, that comprises an engine generator having an engine unit with an engine, and a power generating body mounted on the engine unit and driven by the engine. An adapter to which the power generating body is detachably attached is provided between the drive unit and the power generating body so as to allow replacement of the power generating body.
In the above-mentioned engine generator, it is preferable that the adapter has a common mounting portion to which a plurality of power generating bodies are singularly mountable, the power generating bodies having control systems different from one other.
Namely, in a preferred embodiment, a power generating body based on a control system which is different from a control system of an existing power generating body is allowed to be attached to the engine unit with the aid of the adapter.
In the invention, one replaces the power generating body with another power generating body by a simple replacing work. Accordingly, whenever occasion calls, one can replace the power generating body with another power generating body, and change the product specifications to other ones. Therefore, in a specific example, one can replace a power generating body of the AVR type with another power generating body of the inverter type. Accordingly, there is no need for the alternative manufacturing and purchasing, and the invention succeeds in eliminating the excessive stock or shortage of merchandize in stock.
In addition to this, it is also an object of the present invention to provide an engine generator which allows the power generating body to be disposed on the engine output shaft without altering the engine side, such as a crank shaft.
The object can be achieved by an engine generator, according to a second aspect of the present invention, comprising an engine and a power generating body driven by the engine. A flywheel, a cooling fan driven by the engine, a recoil device for starting up the engine, and the power generating body are disposed the side of the engine having an output shaft, and arranged in this order from the engine.
In the engine generator, an adapter to which the power generating body may be attached is provided at the tip end of a crank shaft of the engine. In this case, in a structure where the flywheel is mounted on the output shaft, an adapter is mounted on the flywheel, the power generating body and the crankshaft as the output shaft are coupled with each other with the aid of the adapter.
In the invention, the component parts are thus laid out, the power generating body and the engine are both cooled by use of one cooling fan. Further, the power generating body is mounted on the output shaft with the help of the adapter. Accordingly, there is no need of using the long crank shaft exclusively used for the engine generator, and the component parts may be laid out as stated above without any alteration in the engine side. Accordingly, a general purpose engine may be applied to the engine generator without using any dedicated part for the crank shaft, and the production cost is reduced. Since the power generating body is fastened by using the adapter, a sufficient large diameter of the coupling part is secured. Those may be coupled together at sufficient strength.